(1) Field of the Invention
This invention relates to turbochargers driven by exhaust gases of an internal combustion engine, and more particularly it is concerned with a variable-capacity turbocharger capable of varying its capacity in accordance with the operating condition of the engine.
(2) Description of the Prior Art
Two types of variable-volume turbochargers have hitherto been known. They include:
(1) One type having a valve body located upstream of the turbine and including an exhaust flow control valve as disclosed in Japanese Patent Unexamined Publication No. 120014/78; and
(2) The other type having an exhaust flow control valve located within the exhaust manifold, as disclosed in Japanese Patent Unexamined Publication No. 118521/81.
These two types of variable-capacity turbochargers of the prior art have encountered the following problems. The turbocharger of type (1) including the valve body becomes large in overall size, making it quite difficult to mount it in a small size passenger automotive vehicle without effecting extensive alterations in design in the engine and accessory equipment.
Meanwhile in the case of the turbocharger of type (2), the arrangement whereby the exhaust flow control valve is mounted in such a manner that it closes in the direction of flow of exhaust gases requires a high drive force when the flowrate of exhaust gases suddenly increases as when the engine is accelerated.